Ken Weatherwax, who played Pugsley in the original Addams Family, has died at the age of 59.
The actor suffered a heart attack and was found at his home in California on Sunday.
Pugsley was the oldest child of Gomez and Morticia Addams in the 1960s TV series.
The show featured a family of macabre oddballs who believed they were normal, and was famed for its catchy finger-snapping theme song.
The dysfunctional family were first created by cartoonist Charles Addams in the New Yorker magazine.
The characters were made into a TV show, which aired on ABC from 1964 to 1966, had a total of 64 episodes.
Weathermax, who also voiced the role of Pugsley in an animated version of the series in the 1970s, played Pugsley senior in a TV special Halloween With the New Addams Family in 1977..